Oilfield tubulars are disposed into boreholes, e.g., wellbores, to perform various tasks. In some applications, a centralizer may be disposed with, e.g., on, a tubular to laterally position the tubular within the borehole, for example, to position the tubular adjacent but spaced from the wall of the borehole (which may be in the ground itself or the inner wall of an outer tubular such as a casing, liner, etc. in the ground). A centralizer is commonly utilized to maintain separation, e.g., 360 degrees of “stand-off” from the borehole wall, between the tubular and the borehole to allow cement to be disposed in the annulus formed therebetween. Centralizing may dispose a tubular coaxial with a borehole. Centralizers may include a pair of collars that are interconnected with collapsible bows allowing passage through restrictions. Centralizers are generally retained on the tubular with the tubular extending through the respective bores of the collars and the array of bows extending radially outward from the tubular string to provide the desired stand-off. The term restriction is used generally herein to describe a reduced inside diameter portion of borehole. The restriction may be formed intentionally (e.g., an inner diameter transition) or unintentionally (e.g., dogleg, turn, sloughing, etc.).
Many wells, e.g., horizontal wells, present restrictions of very tight clearance (i.e., close tolerance) between a tubular having an external centralizer and a section of the borehole, e.g., the section where the borehole is the outer tubular of two concentric tubulars (casing strings) or where the borehole contains another restriction (e.g., a window milled into the side of the outer concentric tubular for the inner tubular to exit). For example, an inner tubular having an outer diameter of 11⅞″ being run inside an outer tubular having an inner diameter of 12.3″ (and an outer diameter of 13⅜″) creates only 0.425″ clearance on the diameter, i.e., 0.425″ of positive outer diameter (OD) clearance and 0.2125″ of radial thickness. Once the tubular with the centralizer disposed on it exits a “close tolerance” section (e.g., where the bows are substantially, fully collapsed), it is generally desired for the collapsed bows to elastically return to their pre-collapsed state. A failure to elastically return to their pre-collapsed state may cause the bows to not properly centralize the tubular and thus the tubular contacts the borehole wall and cement does not fully encircle the tubular to be centralized, which may lead to failure of the well.